The present invention relates to a method for producing an ectoprotein translated from the hepatitis C viral genome and more specifically to a method for producing a glycoprotein called first envelope protein (hereinafter referred to as "E1" protein) which is encoded by the hepatitis C virus (hereinafter referred to as "HCV") gene and which would be used as a material for preparing an HCV vaccine and as a diagnostic agent for detecting an anti-HCV envelope protein antibody.
In 1988, Chiron Co., Ltd. U.S.A. performed cloning of a novel human hepatitis virus conventionally called hepatitis non-A non-B virus and named it "HCV" and developed an agent for diagnosing C type hepatitis comprising a fused protein (C100-3) which is produced by a recombinant yeast cell transformed with a plasmid carrying a fragment of the HCV gene and a gene coding for human superoxide dismutase (SOD) and which is composed of a peptide encoded by the fragment of the HCV gene and human superoxide dismutase (SOD). The use of the diagnostic agent, accordingly, makes it clear that 71% of the post-transfusion hepatitis and 58% of the sporadic hepatitis are positive for the antibody (Science, 1989, 244, pp. 359-362 and pp. 362-364).
More specifically, it has been believed that the infection with C type hepatitis was caused by blood transfusion or the use of blood derivatives contaminated with the hepatitis virus, but it was proved that the crisis of sporadic C type hepatitis is also observed. This fact indicates, with emphasis, that immunization with a vaccine is effective for preventing infection with the C type hepatitis.
Thereafter, an HCV gene originated from a serum of a Japanese patient was cloned and correspondingly it became clear that the HCV prevailing in Japan was similar to that isolated by Chiron Co., Ltd., but was a strain peculiar to Japan comprising a quite different sequence (Tanpakushitsu Kakusan Koso (Proteins, Nucleic Acids and Enzymes). 1991, 36, pp. 1679-1691). However, the difference in antigenicity between the Japan strain and the U.S. strain has not yet been clarified. Moreover, the serotype of the HCV is believed to be only one irrespective of the diversity of the amino acid sequences thereof.
The foregoing C100-3 antibody-detecting system is proved to be insufficient in the rate of detection and detection sensitivity. For this reason, there have presently been used, as effective antigens for detection, mixtures of proteins such as proteins present in the core, NS3 and NS5 regions as diagnostic agents of secondary generation, but antibody-detecting systems for individual viral proteins have not yet been established at all. Therefore, there has been desired for the development of novel agents and methods for detecting or diagnosing HCV infection. Moreover, any vaccine for preventing infection with HCV and therapeutic agent for C type hepatitis have not yet been developed at all.